The present invention relates to improvements in a method of injecting a back filling injection material in a shield-forming process.
One object of the present invention is to provide an improvd method of injecting a back filling injection material in a shield-forming process in which the injection of the back filling injection material can be achieved automatically and exactly by means of a simple apparatus.
A method of injecting a back filling injection material in a shield-forming process, is presented wherein an injection pump is reversely rotated so that the back filling injection material will fill a hopper connected by a delivery hose to the intake port of the pump. Subsequently, an upper limit pressure and a lower limit pressure for the injection pump are preset for injecting the back filling injection material, and then, the injection pump is rotated in its forward direction to deliver the back filling injection material to the desired location around the shield through the delivery hose. After completion of the injection filling of the back filling injection material at the desired location the, injection pump is again reversely rotated so that to intake it can take in water within a shield through the delivery hose, and thereby effecting washing of the delivery hose and the injection pump.
In the present invention, since the hopper is connected to the intake port of the injection pump, which is preferably a screw pump or the like, the back filling injection material is sucked and charged into the hopper through a delivery hose connected to a delivery port of the injection pump by simply reversing the rotational direction of the pump. Thus charging the back filling injection material into the pump hopper is achieved in a simple manner. Furthermore, since the hopper is directly connected to the injection pump for the back filling injection material, space is saved and a workability is improved.
In addition, since an upper limit and a lower limit for the injection pressure of the back filling injection material delivered by the injection pump is preset depending upon the ground conditions and before the back filling of the injection material is begun, when the injection pressure, during the back filling reaches the upper pressure limit the pump stops when it reaches the lower pressure limit the pump starts; and when the hopper is empty, the pump stops.
Therefore, according to the present invention, damage to the segments, tail seal, and the like caused by excessive injection pressure of the back filling injection material can be prevented and also, since selection of the back filling injection material can be made over a broad range, leakage of the back filling injection material from various portions can be appropriately dealt with. Furthermore, in prior art filling processes often times a pulsating pressure is applied to the ground by the pumping and this results in the ground's destruction when the back filling material is injected thereinto. Whereas, in the process according to the present invention, pulsating pressure is not applied to the ground and, thus, stable injection of a back filling material is achieved.
Once the injection of the back filling injection material around the shield has been completed in the above-described manner according to the present invention, water within the shield is sucked by the pump through its delivery hose by reversely rotating the pump. Thereby the injection pump and the delivery hose are washed in a simple way. Furthermore, since the wash water is collected in the hopper connected to the pump, the time consuming job of cleaning mortar and the like adhering onto the inside of the shield can be spared by merely transporting the hopper containing the water and the pump out of a tunnel. As described above, the present invention provides many advantages.